JPH0539015A - Circuit structure for use in anti-lock brake system - Google Patents

Abstract

PURPOSE: To largely diminish the influence of an engine stall torque on the control of an anti-lock system having only few sensors. CONSTITUTION: A circuit configuration used for an anti-lock brake system is equipped with a monitoring circuit 7 that controls the wheel sensors positioned on the driven wheels. The monitoring circuit 7 triggers a test cycle (duration TTEST) when two wheels of a driven axle signal shows instability for more than a predetermined time span (T) during a control cycle. By way of the test cycle, brake pressure is introduced into the wheel brake of the instantaneously slower wheel (v1 , vmin .wheel) of the driven axle. The reaction of the driven wheels to the brake pressure delivered is assessed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an anti-lock brake system, which is equipped with a sensor for determining the rotational movement of a drive wheel, and which detects a vehicle reference speed from a sensor signal. The present invention relates to a circuit configuration used in the system. This car reference speed is
It is used as a reference value to control the brake pressure regardless of the rotational movement of each wheel.

[0002]

Various types of antilock braking systems of this type are generally known. Information about the rotational movement of the wheel and the movement of the vehicle used for antilock control or brake pressure control is obtained by measuring the wheel rotational movement with a wheel sensor and logically combining the sensor signals. An acceleration sensor, a pressure sensor, etc. may be further used. The vehicle reference speed, which is used as a reference speed for determining the rotational movement of each wheel and controlling the brake pressure, is selected by logically combining the wheel sensor signals, and the characteristic information can be obtained in a short time. Is not available for interpolating
n) or extrapolation, which is obtained by physically limiting the speed and acceleration of the vehicle or by limiting the speed ramp to a more appropriate value.

[0003]

Although the quality of control depends on valuable information, a great deal of effort is being made to reduce manufacturing costs by using a minimal number of sensors. As a result of the reduced cost associated with the sensor, it is fundamentally difficult in various situations to accurately convert the measurement signal when little data is available for control. The problem in evaluating the wheel rotation movement measured by the sensor is
It is caused by the wheels coupled to each other and the coupling of the drive motor and the wheels. That is, the drive motor affects the wheel rotation speed, and its stall torque (sta
Due to ll torque), erroneous information or erroneously converted information is generated.

The object of the invention is to significantly reduce the effect of engine stall torque on the control of an antilock system having only a small number of sensors. This problem is particularly important if only two drive wheels of the vehicle are provided with wheel sensors or if all wheels are coupled to the drive shaft and operate in a fairly synchronous manner.

[0005]

To achieve this object, the first one is a monitor circuit of the present invention.
This circuit triggers a test cycle when the two wheels of the drive shaft exhibit instability during a control cycle for more than a predetermined time. On the other hand, this test cycle measures the brake pressure and supplies it to the temporarily slower wheels of the drive shaft. Then, the reaction of the drive wheel to the brake pressure introduction is evaluated and analyzed.

That is, a test cycle is triggered during the control according to the invention when the pressure reduction duration of the two wheels of the drive shaft is so long that the braking pressure is reduced substantially completely. Engine in the test cycle
It is recognized whether the stall torque influences the control. When the coefficient of friction is low, the differential gear (def
The introduction of braking pressure into the wheel brakes of the low speed wheel via the ferential gear) results in a secondary high speed wheel speed increase of this axle. This improves driving stability and lateral guidance of this wheel.

According to the invention, a predetermined time is provided, which is 300 to 800 msec, preferably 400 to 600 msec, after which the test cycle is triggered. The sequence of pressure increase pulses
Brake pressure is introduced during this test cycle and the reaction of the wheels to this brake pressure introduction is transformed.

Furthermore, when the rotational tendency of the drive wheel is determined, the already triggered test cycle ends immediately. In addition, the speed of the low speed wheel is, for example, 10 to 20.
Monitoring operation (m
onitoring) is started.

In another embodiment of the invention, during the test cycle, an increase in the brake slip of the pressurized wheel and a concomitant decrease in the brake slip of the second wheel (in the case of an all-wheel drive vehicle). 3.) The reduction in brake slip of other drive wheels is evaluated as indicating high stall torque and low coefficient of friction. The preceding relatively long pressure decrease is evidence of a low coefficient of friction. In this case, it is confirmed by the influence of the difference.

An increase in the brake pressure of the pressurized wheel during the test cycle and a corresponding lack of recoil, ie a reduction of the brake slip of the other drive wheel, is evaluated as a vehicle reference speed that is too high. The vehicle reference speed may be set too high due to incorrect adjustment or malfunction of additional sensors, or other effects. Vehicle reference speeds that are too high are in this case calibrated by approximation of the reference speed with respect to v _min · wheel.

Finally, the pressurized wheel and / or
The brake slip of the other drive wheels remains constant during the test cycle. This is evaluated by the present invention as evidence of a relatively high coefficient of friction or friction of different nature.

Other preferred embodiments are indicated by the dependent claims.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 and FIG.
For vehicles with only a single drive shaft, two wheel sensors are provided. The output signal indicates the rotational movement of the two drive wheels. A sensor may be added to respond once when the vehicle exceeds a certain deceleration threshold. Control can be significantly improved by using such a vehicle sensor, in particular the vehicle reference speed can be more accurately adapted to the respective situation, but such a sensor is provided in the following operating modes: There is no. The function of such a sensor is similarly monitored by the circuit arrangement of the present invention.

FIG. 1 shows the speed variations v ₁ , v ₂ of two drive wheels under controlled braking, under a relatively low coefficient of friction. The vehicle reference velocity v _REF, which is formed in the general way, is also shown. After the anti-lock control has been started, the initial reference speed in this case follows that of the fastest car wheel (v _max · wheel). The reduction of the vehicle reference speed is then limited to a predetermined limit value, for example -1.3 g, where g is a constant of acceleration due to gravity. This limit value has an effect at time t ₀ . This is because the deceleration of both wheels exceeds this limit at this point and the wheels become unstable. As can be seen from the pressure change with respect to the axis which is also shown in FIG. 1, the reduction of the brake pressure starts at time t ₀ . ”
P ₁ , ₂ ″ represents the pressure change of both wheels and is the same at the beginning. The curve starting at time t ₁ shows the pressure change P ₁ of the low speed wheel, the speed of which is referred to as v ₁ . The hatched portion of the curve shows that the pressure change P ₁ is related to the wheel of speed v ₁ .

However, the reduction of the brake pressure in this case is
It does not cause recovery or reacceleration of the drive wheel during the predetermined time T. Thus, in accordance with the present invention, the test cycle is triggered at time t ₁ to detect the cause of the continued instability and to be properly inserted in the course of control. The test cycle during the time T _Test aims at observing the brake pressure generation by the test pulse train and the reaction to this brake pressure generation. The brake pressure is momentarily slow during this test cycle, ie, v _min
-Introduced only to the wheel brake of the wheel. Figure 1
At, the speed of this wheel is denoted as v ₁ .
In the same situation, a relatively small wheel / road friction coefficient is involved and the introduction of pressure results in this v _min ·
Increases wheel brake slip and results in a decrease in speed v ₁ . In contrast to this, the speed v of the second wheel
₂ increases considerably due to the effect resulting from the difference, ie the effect of compensating the force between the two drive wheels, and approaches the vehicle reference speed v _REF . In FIG. 1, the wheel exhibiting speed v ₂ has increased stability, where the lateral g
uide force) is generated. If the vehicle is front-wheel drive, the steering performance of the vehicle is
And is further improved by reducing the slippage of the unpressurized wheel. An increase in slip at the wheels which is pressurized at time t ₂ which indicates the end of the test cycle, and reduced slippage in the second wheel of the shaft is shown in Figure 1 as Delta] v ₁ and Delta] v _2.

Unstable movement of the two wheels due to very long slip phase and engine stall torque is
It is obtained from the velocity curve of FIG. 1 and the response of the test cycle. The brake pressure introduced during the test cycle remains constant after time t ₂ . That is, the response or introduction of pressure in the test cycle caused by the operation shown in FIG. 1 is typical of low coefficient of friction and high engine stall torque "MSM". During the test cycle, relatively low pressures are rarely introduced when the coefficient of friction is high.

After the "MSM" is recognized, the braking pressure p ₁ introduced on the low speed wheel is kept constant until a second instability occurs on the high speed wheel, whereby the fast wheel (speed v ₂ ) Is stabilized by the effect of the difference. This condition applies at time t ₃ in the situation illustrated by FIG.

FIG. 1 shows the wheel speed change v'under other conditions.
₁ shows a v _'2 (dashed line). In this case, the two drive wheels react faster to the introduction of the brake pressure than in the previous example. The increase in brake pressure caused by the test pulse triggered during the test cycle is
It terminates once immediately after M "is detected. In FIG.
This pressure change p ₁ is shown by the chained branch of the brake pressure curve which transitions to a constant phase at time t _E. "MS
The M "recognition is applied once to the slip changes Δv ₁ and Δv ₂ ,
Then, Δv ′ ₁ and Δv ′ ₂ reach predetermined values. In Example, Δv _1, Δ'v ₁ is limited to 10 km / h, whereas Δv _2, Δv' ₂ is limited to 5km / h.

FIG. 2 shows the response of the wheel during the test cycle and shows the long slip phase T (in contrast to the condition of FIG. 1).
Shows the situation that is not dependent on a large engine stall torque. At time t ₁ , the introduction of braking pressure on the slower wheel (v _min , wheel again shown as v ₁ ) causes an increase in the slippage of the pressurized wheel in this case, while the difference effect does not. The speed v ₂ of the second drive wheel remains the same or decreases, as shown here.
The vehicle reference speed v _REF is too high in a condition that is temporarily caused by over-turning of the wheel prior to braking.
At time t ₂ at the end of the test cycle, the reference speed v _REF decreases to the speed v _{1 of the} slow wheel. Brake pressure control is continued independently for each wheel.

The reduction of the too high reference velocity v _REF at the time t ₂ in the situation shown in FIG. 2 is an important safety measure. This is because a vehicle reference speed that is too high will cause a large amount of brake slippage and the control will respond to reduce brake pressure.

The fact that there is no effect due to the difference in brake pressure during the test cycle as described above may be due to a system error. v _min -When the reduction of the reference speed with respect to the speed of the wheel shows no effect, the antilock control is deactivated in order to protect the braking function.

In the preferred embodiment of the present invention, the test cycle is triggered only when a predetermined minimum speed is exceeded. In this case, the start of the test cycle is only allowed when the speed of the slow wheel exceeds 10 km / h.

Monitor time T is 400 to 500 msec
It has been found that it is appropriate to preset to. If both drive wheels are slipping during this time T, the test cycle is triggered and its duration T _Test can be set, for example, between 150 and 300 msec. At this test cycle or at the end of this cycle, the response of the drive wheel can be determined for each state and for the measurement of the appropriate control. Control is achieved in this way without using those data that cannot be supplied by the sensors on the non-drive wheels.

FIG. 3 shows the most important circuit parts in the present invention. While the circuit blocks shown above the dashed line are generally necessary parts, the module units shown below this line are necessary to perform test cycles, determine engine stall torque, and adapt control. Therefore, the monitor circuit 7 is formed.

The circuit configuration shown in FIG. 3 has two sensors S1,
An anti-lock braking system with only S2 is intended, but an all-wheel braking system with four sensors S1 to S4 is also contemplated.

This circuit configuration comprises a signal processing unit 1, to which the output signals of the wheel sensors S1, S2 or S1 to S4 are supplied. Car reference speed v _{RE F} is formed by the circuit block 2 from the velocity signal processed (in a certain state to receive the support of other sensor signals that are not shown here). The brake pressure control signal is generated in the control logic 3, which has the processed sensor signal, the v _REF signal and the signal _fed back via the bundle 4 of lines. The valve control 5 including the actual brake pressure control valve and the valve block 6 are also shown.

The monitor circuit 7 (later described a system with only two sensors S1 and S2) comprises a multiplex unit 8. This unit 8 supplies the reference speed v _REF formed by the circuit block 2 or the low wheel speed v _min determined by the comparator 9 to the control logic 3.

Once the reference speed v _REF exceeds v _MAX ,
That is, when both v ₁ and v ₂ are exceeded, an output signal is generated in the comparator 10. v _MAX is determined by the multiplex unit 11.

That is, once v _REF exceeds v _MAX , the maximum slipping phase and the time element 12 indicating the predetermined monitoring time T are started (see FIGS. 1 and 2). The other time element 13 is connected to the output of the time element 12. because,
This is because the test cycle T _Test follows after the monitoring time interval T has elapsed. Through the AND gate 14, this test cycle triggers a test pulse, which is generated in the clock generator 15 and supplied to the circuit 16. The circuit 16 is arranged in the signal path from the control logic 3 to the valve control 5, and the AND gate 14
At the beginning of a test cycle of duration T _Test , a pulsed introduction of brake pressure is generated when there is an output signal at.

In order to detect the engine stall torque "MSM", the output of the time element 12 is passed through two parallel memory units 17, 18 to the comparators 19, 20.
Is supplied to. These memory units store high and / or low instantaneous wheel velocities v ₂ , v ₁ . These comparators are the actual speeds v ₂ and / or v ₁
, And the corresponding stored value v _2M , and v ₁ and v _1M , and an output signal is generated when a predetermined limit value is exceeded. The magnitude of this value depends on the "offset" input. Whether or not the engine stall torque "MSM" is obviously generated or has come to be influenced is finally recognized by the output signal of the AND gate 21, and the AND gate 21 is provided with two comparators 19 and 2.
An output signal of 0 is provided. When "MSM" is detected, the AND state at the input of AND gate 14 is immediately removed by inverter 22 to stop providing additional pressure during the test cycle.

The reset of the time elements 12 and 13 is OR
This is done through the gate 23. It is a comparator 10
Is when the output of ends. Because comparator 1
The output signal of 0 passes through the inverter 24 and the OR gate 23.
It is because it is supplied to. In this case, the reset is triggered when the reference speed v _REF is less than the high wheel speed v _MAX . Otherwise, it is triggered when the reference speed is less than the high wheel speed v _MAX . Furthermore, O
The R gate 23 is driven by an AND gate 25 which couples the "MSM" signal to the output signal of the control logic.
This output signal is generated at time t ₃ (see FIG. 1) when the stabilized wheel, namely the v _MAX wheel (v ₂ in FIG. 1) becomes unstable during the second time from t _0. Occur. v _{MA X} · pressure wheel pressurized to ensure the stability of the wheel is reduced again after t ₃ by the influence of the difference.

The third input of the OR gate 23, which can trigger the resetting of the time elements 12, 13, is the comparator 26.
Of the reference speed v
_REF is a predetermined speed threshold or, for example, 10 km /
Below a "offset" threshold, such as h, a signal is provided indicating that.

Brake pressure is introduced into the wheel brakes of the slower wheels, ie v _min · wheels, during the test cycle. Therefore, the circuit 16 has the flip-flop 2
It is driven by the comparator 9 via 7. This flip-flop is reset immediately after the monitor time T has expired. Simultaneously with the resetting of the flip-flop 27, the speeds v ₂ and v ₁ are as described above, the memory unit 17,
18 is stored.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in wheel speed and a change in brake pressure when a test cycle is triggered under one condition.

FIG. 2 is a diagram showing a change in wheel speed and a change in brake pressure when a test cycle is triggered under another condition different from that in FIG.

FIG. 3 is a block diagram showing the most important components in the present invention.

[Explanation of symbols]

v _REF … Car reference speed, T _Test … Test cycle, P ₁ ·
P ₂ ... Wheel brake pressure, v ₁ v ₂ ... Wheel speed, 1 ... Signal processing unit, 3 ... Control logic, 6 ... Valve block, 7 ... Monitor circuit, 9/10/19/20
26 ... Comparator.

Front Page Continuation (72) Inventor Rolf Schieupet, Federal Republic of Germany, 6293 Leinberg-Obershausen, Hauptschütlerse 18 (72) Inventor, Thomas Schyutrigel, Federal Republic of Germany, 6237 Leader Basch, Zum Morgengraben 16 ( 72) Inventor Harald Karl, Federal Republic of Germany, 6250 Limburg 3, Diudentensiyutrase 26 (72) Inventor Thomas Preger, Federal Republic of Germany, 6074 Radarmark 1, Gesyubinster-Sjoulesyutrase 25 (72) Inventor Wolfgang Clink Germany, 6000 Frankfurt / Main 90, Langer Beek 17

Claims (11)

[Claims] 1. A vehicle for use in an anti-lock braking system having a sensor for determining a rotational movement of a drive wheel, the vehicle being used as a reference value for controlling a brake pressure from a signal of the sensor. A circuit is provided to obtain the reference speed independently of the rotational movement of each wheel, and when the two wheels of the drive shaft exhibit instability during a control cycle for more than a predetermined time interval (t), a test cycle ( A circuit that triggers a duration T _Test ),
And that the test cycle measures the brake pressure and temporarily provides it to the wheel brake of the low speed wheel (v _min · wheel), and the reaction of the drive wheel to the introduction of the brake pressure is inspected and analyzed. Characteristic circuit configuration. 2. The time interval for triggering the test cycle is 300 to 800 msec, preferably 40.
The circuit configuration according to claim 1, wherein the circuit duration is 0 to 600 msec. 3. The circuit arrangement according to claim 1, wherein during the test cycle, the brake pressure is introduced by a sequence of pressure increasing pulses, and a reaction to the introduction of the pressure is determined. 4. The test cycle is 50 to 500 mse
c, a duration (T, preferably in the range of 150 to 300 msec)
_4. The circuit configuration according to claim 3, wherein the circuit configuration is limited to _Test ). 5. The circuit arrangement according to claim 1, wherein the test cycle is terminated when the rotation characteristic of the drive wheel is determined. 6. The monitoring is for a slow drive wheel (v _min.
6. Circuit arrangement according to one of the claims 1 to 5, characterized in that it is set from the function when the speed of the wheels) is below a predetermined limit value, for example 10 to 20 km / h. 7. An increase in brake slip on the pressurized wheel and a concomitant decrease in brake slip on the second wheel and other drive wheels during the test cycle (T _Test ) is compared. 7. Circuit arrangement according to claim 1, characterized in that it is evaluated as exhibiting a relatively high engine stall torque and a relatively low coefficient of friction. 8. Increased brake pressure on the pressurized wheel during the test cycle (T _Test ) and lack of recoil for the other drive wheels is an indication of a vehicle reference speed (v _REF ) that is too high. The circuit arrangement according to one of claims 1 to 7, characterized in that it is evaluated. 9. The too high vehicle reference speed (v _REF ) found in the test cycle is calibrated by approximation of the reference speed for the temporarily slowest drive wheel (v _min · wheel). The circuit configuration according to claim 8, which is characterized in that. 10. If the brake slip on the pressurized wheel and / or the brake slip on another drive wheel maintains a constant value during the test cycle, this results in a high coefficient of friction or a different coefficient of friction. 9. The circuit arrangement according to claim 8, characterized in that it is evaluated as indicating an accompanying condition or as indicating an error in the system. 11. The introduction of pressure during the test cycle (T _Test ) is only up to a specific reaction and until a change in predetermined brake slip occurs on the pressurized wheel and the other drive wheel. 8. Circuit arrangement according to claim 7, characterized in that the braking pressure is kept constant until the next instability of the faster wheel (v _max · wheel) occurs.